1、Designation: E 782 95 (Reapproved 2007)Standard Practice forExposure of Cover Materials for Solar Collectors to NaturalWeathering Under Conditions Simulating Operational Mode1This standard is issued under the fixed designation E 782; the number immediately following the designation indicates the yea
2、r oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice provides a procedure for the exposure of
3、cover materials for flat-plate solar collectors to the naturalweather environment at temperatures that are elevated toapproximate operating conditions.1.2 This practice is suitable for exposure of both glass andplastic solar collector cover materials. Provisions are made forexposure of single and do
4、uble cover assemblies to accommo-date the need for exposure of both inner and outer solarcollector cover materials.1.3 This practice does not apply to cover materials forevacuated collectors or photovoltaics.1.4 The values stated in SI units are to be regarded as thestandard.1.5 This standard does n
5、ot purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standar
6、ds:2E 781 Practice for Evaluating Absorptive Solar ReceiverMaterials When Exposed to Conditions Simulating Stag-nation in Solar Collectors With Cover PlatesE 881 Practice for Exposure of Solar Collector Cover Ma-terials to Natural Weathering Under Conditions SimulatingStagnation ModeG7 Practice for
7、Atmospheric Environmental ExposureTesting of Nonmetallic Materials3. Significance and Use3.1 This practice describes a weathering box test fixture andprovides uniform exposure guidelines to minimize the vari-ables encountered during outdoor exposure testing.3.2 This practice may be useful in compari
8、ng the perfor-mance of different materials at one site or the performance ofthe same material at different sites, or both.3.3 Since the combination of elevated temperature and solarradiation may cause some solar collector cover materials todegrade more rapidly than either alone, a weathering box tha
9、televates the temperature of the cover materials is used.3.4 This practice is intended to assist in the evaluation ofsolar collector cover materials in the operational, not stagna-tion mode. Insufficient data exist to obtain exact correlationbetween the behavior of materials exposed according to thi
10、spractice and actual in-service performance.3.5 Means of evaluation of effects of weathering are pro-vided in Practice E 781, and in other ASTM test methods thatevaluate material properties.3.6 Tests of the type described in this practice may be usedto evaluate the stability of solar collector cover
11、 materials whenexposed outdoors to the varied influences which compriseweather. Exposure conditions are complex and changeable.Important factors are solar radiation, temperature, moisture,time of year, presence of pollutants, etc. These factors varyfrom site to site and should be considered in selec
12、ting locationsfor exposure. Control samples must always be used in weath-ering tests for comparative analysis. Outdoor exposure for atleast two years is required to make evident changes, such assurface degradation without the use of sophisticated analyticalequipment.3.7 Temperature conditions attain
13、ed with this box may notexactly duplicate those that occur under operational conditionswith fluid flow. Dependent on environmental exposure condi-tions, the cover plate temperatures obtained with this box maybe higher or lower than those obtained under operationalconditions. Additional testing under
14、 stagnation conditions,although not covered by this practice should be conducted.NOTE 1Research has shown that exposure outdoors at sites having thecombination of high levels of humidity, solar energy, and ambient1These test methods are under the jurisdiction of ASTM Committee E44 onSolar, Geotherma
15、l and Other Alternative Energy Sources and is the direct respon-sibility of Subcommittee E44.05 on Solar Heating and Cooling Systems andMaterials.Current edition approved March 1, 2007. Published April 2007. Originallyapproved in 1981. Last previous edition approved in 2001 as E 782 95 (2001).2For r
16、eferenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
17、West Conshohocken, PA 19428-2959, United States.temperature can cause more severe degradation of some polymeric covermaterials, (for example, microcracking and leaching of UV radiationscreening additives) than exposure in arid climates.NOTE 2Stagnation conditions are a normal occurrence for solarcol
18、lectors, for example, during operation when the storage is fullycharged; when the collectors are initially installed, before system start-up;or when the system is shut down for maintenance or seasonal consider-ations such as heating only systems in the summer.4. Weathering Box Test Fixture4.1 Weathe
19、ring Box Test Fixture, consisting of a box, rails,a box top, a glazing frame, and adhesive tapes. The weatheringbox test fixture should be constructed in accordance with Figs.1-5.4.1.1 The box and box top should be made in metal that issuitably resistant to corrosion encountered in the exposureenvir
20、onment. A weep hole should be drilled at the lower end ofthe bottom of the box to provide drainage and to minimizemoisture accumulation.NOTE 3The box top is intended to protect the edges of the testspecimen in contact with the box from reaching excessively hightemperatures, to minimize exposure of t
21、he adhesive to sunlight, and tominimize moisture penetration into the exposure test fixture.4.1.2 The box interior shall be a flat black nonselectivecoating having an absorptance of not less than 0.90 afterexposure. Organic absorber coatings should be heated in anoven at 150C (302F) for 24 h before
22、the test fixture isasssembled. This should minimize outgassing, which resultsNOTE 1Material: metal suitably corrosion-resistant for exposure. Atypical material would be 24-gage galvanized steel.NOTE 2Dimension tolerance 61mm(6116 in.).NOTE 3Box must be watertight when weep hole is covered.NOTE 4Pain
23、t interior of box black, bake1hat150C.NOTE 5Use lead solder on corner joints.FIG. 1 Natural Weathering BoxBoxNOTE 1Make: 4 per box.NOTE 2Material: metal suitably corrosion-resistant for exposure. Atypical material would be 24-gage galvanized steel.NOTE 3Dimension tolerance 61mm(6116 in.).FIG. 2 Natu
24、ral Weathering BoxRollsNOTE 1Make: 1 per box.NOTE 2Material: metal suitably corrosion-resistant for exposure. Atypical material would be 24-gage galvanized steel.NOTE 3Top must fit over box with rails in place.FIG. 3 Natural Weathering BoxTopE 782 95 (2007)2from deterioration of the organic componen
25、ts exposed toelevated temperatures.4.1.3 The adhesive tapes should be stable when exposed tomoisture and elevated temperatures. They should be compat-ible with the specific materials from which the box, glazingframe, box top, and cover plate are made.4.1.4 Organic materials are potential sources for
26、 outgassingand should be eliminated from the interior of the weatheringbox where possible. For example, metallic parts should becleaned to remove traces of grease or other foreign matter.Other possible sources of outgassing include coatings andsealants. Section 4.1.2 addresses outgassing of absorber
27、 coat-ings.4.2 Test Specimen:4.2.1 The test specimen shall be of an adequate size to coverthe aperture of the box or glazing frame, and considerationgiven to dimensional changes due to temperature.4.2.2 The test specimen identification marks shall not inter-fere with either the exposure or the subse
28、quent testing.4.3 Sample Mounting:4.3.1 Rigid and Semirigid Glazings:4.3.1.1 Lay test specimens for single cover exposure di-rectly on the glazing frame and place the frame on the rails inthe weathering box (see Fig. 5).4.3.1.2 Lay test specimens for inner cover exposure on adouble cover assembly on
29、 the rails before the glazing frame isput in place (see Fig. 5).4.3.1.3 Lay test specimens for outer cover exposure on adouble cover assembly on the glazing frame (see Fig. 5).4.3.2 Films:4.3.2.1 Place film test specimens on the glazing frame usingadhesive transfer tape to hold the test specimens ta
30、ut. Thenplace the frame in the box (see Fig. 5) similar to 4.3.1.1,4.3.1.2, and 4.3.1.3.4.4 Assembly of Weathering Box:4.4.1 Slide the various parts of the weathering box testfixture into position. The outer glazing must be roughly flushwith the top side of the box. The position of an inner glazing,
31、if used, will be nearest the bottom of the box. If an innerglazing of substantial thickness is used, the frame may protrudeabove the box edge by an amount equal to the thickness of theglazing.4.4.2 After assembly, seal the frame and outer glazing inplace with an adhesive tape to prevent moisture int
32、rusion. Thenplace the cover on the box covering the tape (see Fig. 5).5. Natural Weathering Exposure5.1 Mount the weathering boxes in a backed condition(using 13-mm (12-in.) exterior grade plywood) on weatheringNOTE 1Make: 1 per box.NOTE 2Material: metal suitably corrosion-resistant for exposure. At
33、ypical material would be 24-gage galvanized steel.NOTE 3Glazing frame must fit into box.FIG. 4 Natural Weathering BoxGlazing FrameFIG. 5 Natural Weathering Box AssemblyRigid GlazingE 782 95 (2007)3racks such as those described in Recommended Practice G7.The racks should be capable of having the angl
34、es adjusted andhave their axis of rotation on an east-west line.5.2 Use a variable-angle exposure to maximize solar radia-tion upon the weathering box. Adjust the racks in accordancewith one of the schedules contained in Annex of PracticeE 881.5.3 When a number of weathering boxes are exposedsimulta
35、neously, mount the boxes side by side with the sides nottouching.5.4 Do not clean the solar collector cover materials duringexposure.6. Report6.1 The report shall include the following:6.1.1 Complete identification of the solar collector covermaterial,6.1.2 Whether the solar collector cover material
36、s are ex-posed as a single or double cover configuration and whether thetest specimen was the inner or outer cover,6.1.3 Material used for the absorber coating,6.1.4 Description of the test specimen attachment andmounting procedures,6.1.5 Latitude, longitude, altitude, and address of the testingsite
37、 including a description of the type of climate,6.1.6 Exposure data,6.1.7 Climatological data,6.1.7.1 Radiant exposure (GJ/m2) measured in the plane ofthe weathering boxes,6.1.7.2 Monthly maximum, minimum, and mean tempera-tures,6.1.8 Visual inspection of test specimens, noting any obvi-ous changes
38、in appearance should be made at regular scheduledintervals (once per month minimum),6.1.9 Description of control specimens, and6.1.10 Any deviation from this practice.6.2 Other data that are desirable to report, if available, are:6.2.1 Optional climatological data,6.2.1.1 Daily maximum, minimum, and
39、 mean percent rela-tive humidity,6.2.1.2 Daily hours of wetness, both dew and rain,6.2.1.3 Daily total inches of rainfall,6.2.1.4 Daily maximum and minimum ambient temperature,6.2.1.5 Daily radiant energy,6.2.1.6 Wind direction and velocity,6.2.2 Type of atmosphere, for example, industrial, and leve
40、lof air pollutants,6.2.3 Ultraviolet radiation, and6.2.4 Maximum absorber plate temperature.7. Keywords7.1 aging; cover plates; exposure; natural weathering; solarcollectors; solar collector cover materials; weatheringASTM International takes no position respecting the validity of any patent rights
41、asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any tim
42、e by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will r
43、eceive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM I
44、nternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).E 782 95 (2007)4
